237.1 🎓 醫孞生版

237.1.0.1 📌 䞀頁重點

237.1.0.1.1 Adult Intestinal Tapeworms
Species Source Clinical Treatment
Taenia saginata Undercooked beef Often asymptomatic; mild GI; proglottids in stool Praziquantel single dose or niclosamide
Taenia solium Undercooked pork Similar to above + cysticercosis if eggs ingested Praziquantel + niclosamide
Diphyllobothrium latum Undercooked freshwater fish (pike, salmon — N hemisphere, Mediterranean) Often asymptomatic; B12 deficiency + megaloblastic anemia Praziquantel
Hymenolepis nana Person-to-person fecal-oral (small humans + insects) Mostly asymptomatic; abdominal pain Praziquantel
Hymenolepis diminuta Insect-contaminated grain Mild Praziquantel
237.1.0.1.2 Cysticercosis (Taenia solium Larva)
  • #1 parasitic CNS disease worldwide
  • From ingestion of T. solium eggs (not from pork tapeworm carrier himself, but from contaminated food/water or self-infection)
  • Latin America, sub-Saharan Africa, S Asia endemic
  • Eggs hatch in human → oncospheres invade tissue + form cysticerci
  • Tissue cysts in muscle, brain, eye, subcutaneous
237.1.0.1.2.1 Neurocysticercosis (NCC)
  • Most clinically relevant
  • Etiology of acquired epilepsy worldwide (especially endemic regions)
  • 4 forms:
    • Active: viable cysts + immune attack → seizures, hydrocephalus, mass effect
    • Transitional: degenerating cysts
    • Calcified: inactive (residual)
    • Extraparenchymal: cisternal, ventricular, intramedullary
237.1.0.1.3 Clinical (Neurocysticercosis)
  • Seizures (most common presentation; new-onset adult)
  • Hydrocephalus (cysts blocking CSF flow)
  • Headache + focal neuro
  • Increased intracranial pressure
  • Cognitive / behavioral changes
237.1.0.1.4 Diagnosis
  • MRI brain (most sensitive): viable cysts (T1 hypointense, T2 hyperintense; scolex visible “hole-with-dot” sign); transitional (ring-enhancing); calcified (CT shows calcification)
  • CT brain: detects calcifications well
  • Serology (anti-cysticercus antibody — EITB Western blot most specific)
  • CSF antibody (less reliable)
237.1.0.1.5 Treatment Neurocysticercosis
  • Antiparasitic:
    • Albendazole 15 mg/kg/d PO × 8-30 days OR
    • Albendazole + praziquantel combination (large burden)
  • Steroid (dexamethasone) for inflammatory response to dying cysts
  • Anticonvulsants for seizures (chronic, may continue years)
  • Surgical: shunt for hydrocephalus, resection for symptomatic single cyst, endoscopic for ventricular cysts
  • Endemic public health: deworming + sanitation + pork inspection
237.1.0.1.6 Echinococcosis (Hydatid Disease)
  • Larval cyst infection from dog tapeworm
  • 2 main species:
    • Echinococcus granulosus → Cystic echinococcosis (CE) — solitary cyst, sheep/dog cycle
    • Echinococcus multilocularis → Alveolar echinococcosis (AE) — infiltrative tumor-like, fox/dog cycle, Arctic + Europe
  • Other: E. vogeli, E. oligarthrus (S America, rare)
237.1.0.1.6.1 Cystic Echinococcosis (CE)
  • Dog definitive host, sheep + livestock intermediate
  • Human accidental intermediate host
  • Worldwide: Mediterranean, Mid East, S America, E Africa, China, Central Asia
  • Liver (#1, 70%) + lung + brain + bone + spleen + muscle
  • Slow-growing fluid-filled cyst
  • Multiple daughter cysts within mother cyst (hydatid sand)
  • Asymptomatic many years
  • Sx from mass effect or rupture
  • Rupture → anaphylaxis + dissemination of daughter cysts
237.1.0.1.6.2 Alveolar Echinococcosis (AE)
  • Fox / dog definitive host, rodent intermediate
  • Arctic + sub-Arctic + Central Europe + Western China
  • Infiltrative, tumor-like growth in liver
  • Mimics malignancy
  • Lobar invasion + metastases
  • Untreated fatal
237.1.0.1.7 Diagnosis Echinococcosis
  • Imaging (US, CT, MRI): liver cyst — characteristic appearance
  • Serology (CE-specific; AE-specific)
  • WHO classification of cysts: CE1-CE5 active to inactive
  • AE: PET-CT for staging
237.1.0.1.8 Treatment Echinococcosis
237.1.0.1.8.1 Cystic Echinococcosis (CE)
  • Albendazole 15 mg/kg/d × 3-6 months (or longer)
  • PAIR (Puncture-Aspiration-Injection-Reaspiration) — percutaneous treatment for select cysts
  • Surgical — cyst removal (be careful not to rupture intraoperatively)
  • Observation for inactive CE4/CE5 cysts
  • WHO management based on cyst stage
237.1.0.1.8.2 Alveolar Echinococcosis (AE)
  • Surgical resection (R0) — only curative option
  • Albendazole lifelong (or long-term post-surgery)
  • Liver transplant rare cases
  • PAIR not appropriate (infiltrative)
237.1.0.1.9 Prevention
  • Cook meat thoroughly (beef, pork, fish, etc.)
  • Freeze meat (kills cysticerci, plerocercoids)
  • Hand hygiene
  • Don’t feed dogs raw offal (transmission)
  • Dog deworming in endemic
  • Sanitation
  • WHO MDA programs for endemic

237.1.0.2 1⃣ Adult Intestinal Tapeworms

237.1.0.2.1 Taenia saginata (Beef Tapeworm)
237.1.0.2.1.1 Life Cycle
  • Adult worm in human small intestine (up to 25 m long; live for years)
  • Proglottids (segments) released in stool
  • Cattle ingest eggs → larvae in muscle
  • Human ingests undercooked beef with cysticerci → matures to adult in intestine
237.1.0.2.1.2 Clinical
  • Often asymptomatic
  • Mild GI: abdominal pain, anorexia, mild diarrhea, weight loss
  • Active motile proglottids in stool / underwear (distinctive complaint)
  • Rare: appendicitis-like, intestinal obstruction
237.1.0.2.1.3 Diagnosis
  • Stool O+P (eggs identical between T. saginata + T. solium — species identification by proglottid morphology)
  • Proglottids: T. saginata has > 12 uterine branches per proglottid
  • Stool antigen, PCR
237.1.0.2.1.4 Treatment
  • Praziquantel 5-10 mg/kg PO single dose
  • Niclosamide 2 g PO single dose alternative
  • Sanitation prevents transmission
237.1.0.2.2 Taenia solium (Pork Tapeworm)
237.1.0.2.2.1 Life Cycle
  • Adult in human intestine (similar to T. saginata)
  • Pigs are normal intermediate host (cysticerci in muscle)
  • Human can be both definitive (adult worm from undercooked pork) AND intermediate (eggs → cysticercosis)
  • Major importance: fecal contamination + autoinfection can cause cysticercosis in tapeworm carrier or contacts
237.1.0.2.2.2 Clinical (Adult Worm)
  • Similar to T. saginata — mostly asymptomatic
  • T. solium proglottids: 7-13 uterine branches (vs T. saginata > 12)
  • Risk of cysticercosis to self or others (contact contamination)
237.1.0.2.2.3 Treatment
  • Praziquantel 5-10 mg/kg PO single dose for adult worm
  • Niclosamide alternative
  • Eradication critical (prevent cysticercosis transmission)
  • Concurrent screening for cysticercosis if needed
237.1.0.2.3 Diphyllobothrium latum (Fish Tapeworm)
237.1.0.2.3.1 Source
  • Undercooked freshwater fish (pike, salmon, perch)
  • Endemic: N hemisphere (Scandinavia, Russia, Baltic, Great Lakes USA, Japan, Mediterranean)
  • “Sushi tapeworm” (less commonly from marine fish; mostly freshwater)
237.1.0.2.3.2 Clinical
  • Most asymptomatic
  • Vitamin B12 deficiency (worm competes for B12) → megaloblastic anemia, neurological deficits (rare but characteristic)
  • Mild GI symptoms
237.1.0.2.3.3 Diagnosis
  • Stool O+P — operculated eggs
237.1.0.2.3.4 Treatment
  • Praziquantel 5-10 mg/kg PO single dose
237.1.0.2.4 Hymenolepis nana (Dwarf Tapeworm)
237.1.0.2.4.1 Life Cycle
  • Most common cestode infection worldwide
  • Person-to-person fecal-oral (egg viable in fresh stool)
  • Insects (beetles) can serve as intermediate
  • Internal autoinfection possible (heavy burden in immunocompromise)
  • Pediatric + crowded settings
237.1.0.2.4.2 Clinical
  • Mostly asymptomatic
  • Abdominal pain, mild diarrhea
  • Pruritus
  • Heavy infection: weight loss, irritability
237.1.0.2.4.3 Treatment
  • Praziquantel 25 mg/kg PO single dose (higher dose than other tapeworms; single dose hatches new eggs less effectively)
  • Repeat in 1 week if needed
237.1.0.2.5 Other
  • Hymenolepis diminuta (rat tapeworm): insect-contaminated grain; mild
  • Dipylidium caninum (dog tapeworm): proglottid ingestion (with flea); pediatric exposure
  • Spirometra (sparganosis): undercooked frog/snake/copepod-contaminated water; tissue larva

237.1.0.3 2⃣ Cysticercosis + Neurocysticercosis

237.1.0.3.1 Background
  • Larval form of Taenia solium
  • Egg ingestion (not pork) causes cysticercosis
  • Autoinfection in tapeworm carriers (oro-fecal)
  • Contamination from another carrier (food handler, household)
  • Latin America, sub-Saharan Africa, S Asia, parts of E Europe endemic
  • Major cause of acquired epilepsy in endemic + immigration-affected developed countries
237.1.0.3.2 Life Cycle of Eggs in Human
  1. Eggs ingested (food, water, fingers contaminated by fecal eggs)
  2. Hatch in intestine → oncospheres
  3. Penetrate intestinal wall → bloodstream → tissue
  4. Tissue cysts (cysticerci) form in:
    • Brain (neurocysticercosis)
    • Subcutaneous tissue
    • Muscle
    • Eye
    • Heart (rare)
  5. Cysticerci viable for years → eventually die → degenerate → calcify
237.1.0.3.3 Neurocysticercosis (NCC)
237.1.0.3.3.1 Forms (Del Brutto 2017 Criteria)
237.1.0.3.3.2 Parenchymal NCC
  • Active: viable cysts (T1 hypointense, T2 hyperintense, with scolex; no enhancement)
  • Transitional: degenerating cysts (ring-enhancing, edema)
  • Calcified: dead cysts (calcification on CT)
237.1.0.3.3.3 Extraparenchymal NCC
  • Cisternal (basal cisterns) — racemose form (grape-like, often inflammatory)
  • Ventricular — risk of acute hydrocephalus
  • Intramedullary spinal cord — rare
237.1.0.3.3.4 Clinical
  • New-onset seizures (#1; cortex active or calcified)
  • Hydrocephalus + intracranial hypertension (ventricular, subarachnoid, racemose)
  • Headache + focal neurological signs
  • Cognitive / behavioral changes
  • Ocular (rare): vision loss, decreased vision
237.1.0.3.3.5 Diagnosis
237.1.0.3.3.6 Imaging (Critical)
  • MRI > CT for soft tissue + cysts + scolex
  • CT detects calcifications well (chronic disease)
  • Active: T1 hypo / T2 hyper / no enhancement (viable)
  • Transitional: ring-enhancing with edema (inflammatory)
  • Calcified: cluster on CT (inactive)
  • Number of cysts, location, viability inform Tx
237.1.0.3.3.7 Serology
  • EITB (Enzyme-linked Immunoelectrotransfer Blot) — most specific Ab test
  • 90%+ sensitivity in multi-cyst disease, lower in single-cyst
  • May be negative in calcified-only disease
237.1.0.3.3.8 CSF
  • Pleocytosis (esp. extraparenchymal)
  • Cysticerci Ab less reliable
237.1.0.3.3.9 Differential
  • Tuberculoma (granulomatous mass — biopsy / response to TB Tx)
  • Pyogenic / fungal abscess
  • Primary CNS lymphoma
  • Glioma
  • Metastases
  • Toxo (in HIV)
237.1.0.3.3.10 Treatment
237.1.0.3.3.11 Antiparasitic
  • Albendazole 15 mg/kg/d PO × 10-15 days for most parenchymal disease
  • Albendazole + praziquantel combination for high cyst burden / extraparenchymal
  • Albendazole alone for single-lesion / limited
  • Avoid antiparasitic in calcified-only disease (no benefit)
237.1.0.3.3.12 Steroid (Dexamethasone)
  • Critical adjunct
  • Reduces inflammatory response to dying parasites
  • 6-24 mg/d PO × 2-3 weeks
  • Higher dose for severe / extraparenchymal
  • Start before / concurrent with albendazole
237.1.0.3.3.13 Anticonvulsants
  • Long-term (often years, sometimes lifelong)
  • For seizures
  • Levetiracetam, valproate, carbamazepine common
  • Continue until calcification stable + no seizures × 1-2 yr
237.1.0.3.3.14 Surgical
  • Ventricular shunt for hydrocephalus
  • Endoscopic removal of intraventricular cysts
  • Resection of symptomatic single cyst (rare)
  • Decompression for severe mass effect
237.1.0.3.3.15 Treatment by Form
Form Approach
Single calcified Anticonvulsants only; no antiparasitic
Single viable parenchymal Albendazole 15 mg/kg/d × 10-15d + dex
Multiple parenchymal Albendazole + praziquantel + dex
Subarachnoid / racemose Albendazole + praziquantel + high-dose dex + shunt; long course
Ventricular Endoscopic removal + shunt + albendazole + dex
Spinal Albendazole + dex; surgery for compression
237.1.0.3.3.16 Family Screening
  • Tapeworm carriers in household (stool testing)
  • Treat to prevent ongoing exposure

237.1.0.4 3⃣ Echinococcosis

237.1.0.4.1 Species
  • E. granulosus — Cystic Echinococcosis (CE)
  • E. multilocularis — Alveolar Echinococcosis (AE)
  • E. vogeli, E. oligarthrus — Neotropical (S America rare)
237.1.0.4.2 Cystic Echinococcosis (CE)
237.1.0.4.2.1 Life Cycle
  • Dog definitive host (adult worms in dog intestine)
  • Sheep + cattle + livestock intermediate (cysts in liver, lung)
  • Human accidental intermediate (ingestion of eggs from dog feces or contaminated produce)
  • Worldwide: Mediterranean, Mid East, S America, sub-Saharan Africa, China, Central Asia
237.1.0.4.2.2 Pathology
  • Liver (#1, 70%) + lung (20%) + brain + bone + spleen + muscle
  • Slow-growing fluid-filled cyst (cm-decades to grow)
  • Inner germinative layer + outer laminated layer + outer adventitia (host)
  • Daughter cysts within mother cyst
  • Hydatid sand = protoscoleces in cyst fluid
237.1.0.4.2.3 Clinical
  • Often asymptomatic for years
  • Mass effect: hepatomegaly, biliary obstruction, cough (lung cyst), seizures (brain)
  • Rupture: anaphylaxis + dissemination of daughter cysts → secondary echinococcosis
  • Bacterial superinfection
  • Calcification (inactive cysts)
237.1.0.4.2.4 Diagnosis
  • Imaging (US, CT, MRI):
    • Anechoic cyst with daughter cysts (pathognomonic “honeycomb” or “ball-of-yarn”)
    • WHO classification CE1-CE5 (active CE1-CE2; transitional CE3; inactive CE4-CE5)
    • Calcification on CT (chronic/inactive)
  • Serology (echinococcal IgG): 90%+ sensitivity in CE; cross-reacts with other parasites
  • Aspiration can cause rupture + dissemination — only do for therapy (PAIR) with specific protocol
237.1.0.4.2.5 Treatment (WHO Guidelines)
237.1.0.4.2.6 WHO Cyst Stage Classification
Stage Activity Treatment
CE1 (active, unilocular) Active Albendazole; PAIR if accessible
CE2 (active, multivesicular) Active Albendazole; surgery if accessible
CE3a (transitional, water-lily sign) Transitional Albendazole; PAIR
CE3b (mostly solid) Transitional Albendazole
CE4 (inactive, mostly solid) Inactive Observation
CE5 (calcified, inactive) Inactive Observation
237.1.0.4.2.7 Treatment Options
237.1.0.4.2.8 Albendazole
  • 15 mg/kg/d PO divided × 3-6 months (or longer for multi-cyst, recurrent)
  • WHO essential medicine
  • Side effects: hepatotoxicity, leukopenia, alopecia long course
  • LFT monitoring
237.1.0.4.2.9 PAIR (Puncture-Aspiration-Injection-Reaspiration)
  • For accessible cysts CE1, CE3a (some CE2)
  • Liver mainly
  • Albendazole pre + post-procedure (prevent dissemination)
  • Aspirate cyst → inject scolicidal agent (95% ethanol, 20% saline) → reaspirate
  • Avoid in bone, lung, brain
237.1.0.4.2.10 Surgical
  • Pericystectomy / cystectomy
  • Especially for large, complex, refractory cysts
  • Albendazole pre + post-surgery
  • Risk of intraoperative spillage → dissemination
237.1.0.4.2.11 Observation
  • CE4, CE5 (inactive)
  • Asymptomatic small (< 5 cm) cysts
237.1.0.4.2.12 Liver Transplant
  • For severe complex hepatic disease (rare)
237.1.0.4.3 Alveolar Echinococcosis (AE)
237.1.0.4.3.1 Life Cycle
  • Red fox (definitive host) + dog (definitive in some) + rodent intermediate
  • Arctic + sub-Arctic + Central Europe + Western China + N N. America (Alaska)
  • Human accidental intermediate (ingestion of eggs from fox feces or contaminated berries / wild produce)
237.1.0.4.3.2 Pathology
  • Infiltrative growth (vs unilocular cyst in CE)
  • Liver primary, but can metastasize like cancer
  • Multilocular vesicles, tumor-like
  • Lobar invasion → liver failure
  • Vascular invasion + distant metastasis (lung, brain)
237.1.0.4.3.3 Clinical
  • Mimics liver cancer / cholangiocarcinoma
  • Asymptomatic until late
  • Hepatomegaly, jaundice, weight loss
  • Hilar mass effect
  • Metastatic disease
  • Fatal if untreated (5-yr survival < 30% historically; improved with treatment)
237.1.0.4.3.4 Diagnosis
  • Imaging (US, CT, MRI): infiltrative mass with calcifications + necrotic areas; mimics cancer
  • Serology (Em-specific antigens)
  • PET-CT for staging + viability
  • Biopsy (with care — dissemination risk; PET-CT often staging without biopsy)
237.1.0.4.3.5 Treatment
  • Surgical R0 resection = only curative option (~ 30-40% of cases amenable)
  • Albendazole lifelong (or long-term post-surgery; prevents recurrence)
  • Liver transplant for inoperable disease (rare)
  • PAIR NOT appropriate (infiltrative)
  • 10-year survival: improving (50-80%)
237.1.0.4.4 Prevention Echinococcosis
  • Don’t feed dogs raw offal
  • Dog deworming in endemic
  • Hand hygiene (especially after dog contact, gardening)
  • Sanitation
  • Wild berries (AE)
  • WHO programs in endemic